Ship and sheep, live and leave: English separates a short, relaxed /ɪ/ from a long, tense /iː/. Spanish, Arabic and many other languages have one i sound, so both come out the same.
For /iː/, smile slightly and hold the sound. For /ɪ/, relax your lips and jaw and keep it short, a little closer to the e in bed.
22% of 35,617 scored /iː/ sounds in the SayWhat app were scored red, from at least 6,613 learners.